CLPP inhibition triggers apoptosis in human ovarian granulosa cells via COX5A abnormality–Mediated mitochondrial dysfunction

Abstract

Premature ovarian insufficiency (POI) is characterized by early loss of ovarian function before the age of 40 years. It is confirmed to have a strong and indispensable genetic component. Caseinolytic mitochondrial matrix peptidase proteolytic subunit (CLPP) is a key inducer of mitochondrial protein quality control for the clearance of misfolded or damaged proteins, which is necessary to maintain mitochondrial function. Previous findings have shown that the variation in CLPP is closely related to the occurrence of POI, which is consistent with our findings. This study identified a novel CLPP missense variant (c.628G > A) in a woman with POI who presented with secondary amenorrhea, ovarian dysfunction, and primary infertility. The variant was located in exon 5 and resulted in a change from alanine to threonine (p.Ala210Thr). Importantly, Clpp was mainly localized in the cytoplasm of mouse ovarian granulosa cells and oocytes, and was relatively highly expressed in granulosa cells. Moreover, the overexpression of c.628G > A variant in human ovarian granulosa cells decreased the proliferative capacity. Functional experiments revealed that the inhibition of CLPP decreased the content and activity of oxidative respiratory chain complex IV by affecting the degradation of aggregated or misfolded COX5A, leading to the accumulation of reactive oxygen species and reduction of mitochondrial membrane potential, ultimately activating the intrinsic apoptotic pathways. The present study demonstrated that CLPP affected the apoptosis of granulosa cells, which might be one of the mechanisms by which CLPP aberrations led to the development of POI.

Exploring biomarkers of premature ovarian insufficiency based on oxford nanopore transcriptional profile and machine learning

“…The latest research suggests that inhibiting CLPP can reduce the content and activity of respiratory chain complex IV by affecting COX5A , leading to mitochondrial dysfunction and apoptosis in human ovarian granulosa cells. This indicates the expression and regulatory role of COX5A in ovarian function 29 . Similarly, Mitochondrial cytochrome C oxidase subunit II ( COX2 ) and cytochrome C oxidase subunit III ( COX3 ) were also reported to be significantly downregulated in GV oocytes in aging mice 25 .…”

Mechanisms of mitochondrial dysfunction in ovarian aging and potential interventions

“…It is known that caseinolytic peptidase P(CLPP) is a highly conserved serine proteolytic enzyme and a key enzyme in UPRmt ( 95 ). Currently, it is reported that human CLPP gene mutation has a clinical phenotype of Perrault syndrome or POI ( 96 , 97 ). In animal experiments, CLPP -/- mice showed auditory defects and complete infertility ( 98 ), and the ovarian reserve in mice showed an accelerated state of depletion with age ( 99 , 100 ).…”

“…In animal experiments, CLPP -/- mice showed auditory defects and complete infertility ( 98 ), and the ovarian reserve in mice showed an accelerated state of depletion with age ( 99 , 100 ). The reason maybe that CLPP -/- mice activate the Sirolimus target (mTOR) pathway in vivo ( 99 ), affecting the degradation of aggregated or misfolded cytochrome oxidase subunit 5A(COX5A) ( 97 ), blocking UPRmt, thus affecting the content and activity of complex IV in ETC, accumulating ROS and reducing mitochondrial membrane potential (MMP), and finally activating the internal apoptosis pathway. It follows that mutations in the key gene CLPP, where UPRmt is affected, will lead to ovarian reserve depletion in mice and humans.…”

“… Mitochondrial quality monitoring and ovarian aging(the figure was created with ) (1)mitochondrial fusion: The low expression of MFN1 ang MFN2 in the outer membrane in aging oocyte may affect mitochondrial fusion and inhibit the PI3K-AKT pathway, affecting oocyte-somatic cell communication ( 108 , 109 ); (2) mitochondrial fission: The decreased expression of DRP1 in oocyte may affect mitochondrial function, leading to a decrease in oocyte quality ( 110 ); (3) mitophagy: Mitochondrial autophagy function decreases during ovarian aging ( 117 , 118 ); (4) UPRmt: The decreased expression of CLPP and PGC1α in aging oocyte may hinder the occurrence of UPRmt ( 96 , 97 ). …”

Discovery of a Novel Series of Homo sapiens Caseinolytic Protease P Agonists for Colorectal Adenocarcinoma Treatment via ATF3-Dependent Integrated Stress Response

“…Due to the lack of ATPase activity, HsClpP only exhibits proteolytic activity toward short peptides comprising up to six amino acids . Two HsClpP heptamers interact with the ClpX chaperone to form the ClpXP protein hydrolysis complex, which is capable to degrade specific protein substrates in the mitochondria to achieve protein quality control. , The variety in the recognition of substrates supports the HsClpP to be involved in various mitochondrial physiological activities, including the tricarboxylic acid cycle, the electron respiratory chain, protein import, and metabolic processes. − HsClpP is overexpressed in many types of cancer, where it has been implicated in patient prognosis and survival, including leukemia, colon, ovarian, pancreatic, and endometrial cancers. − Interestingly, both inhibition and activation of HsClpP are effective in killing tumor cells . Mechanistically, HsClpP inhibition leads to the accumulation of misfolded proteins and damaged respiratory chain proteins, which impairs oxidative phosphorylation; hyper-activation of HsClpP mis-degrades the functional proteins and reduces levels of respiratory chain proteins, which perturbs mitochondrial function .…”